Bioavailability of Heavy Metals in Sludge-Amended Soils Ten Years after Treatment

Abstract

The application of municipal sewage sludge to agricultural land has become an established practice in the United States, especially in areas adjacent to major metropolitan centers.¹ The U.S. Environmental Protection Agency (EPA) established guidelines for regulating the application of sludge materials on farmlands in the 1970s.² However, several agricultural experiment stations in the highly urbanized northeastern states, including Maryland, have established their own guidelines for the disposal of sewage sludge on crop lands.^1–3 The primary factors which limit the quantities of sludge that may be applied to an area are the amounts of heavy metals present in a given sludge and the nutrient requirements of the crops being grown.^1,2 The N and P requirements of the crop generally limit the quantity of sludge that can be applied in a given year and the amount of heavy metals applied to soils are commonly used to establish lifetime loading limits.^{1–8,10,13,14}